Well... there is some huge battles raging about oils so let me step in and stir this turd pot and see where it leads..
Before I switched to Amsoil I use to run ATF once a year or so to clean out the gear box.
It did help with shifting.
Since switching to Amsoil 3 years ago I have not had to do it once.
While running ATF is inexpensive and will help clean your trans out I don't feel as though it provides enough of the correct lubrication you need for longevity.
If it were me, I would run the ATF for one ride then switch to a different gear oil.
Amsoil Motorcycle 10/40 synthetic seems to work pretty good.
Recently I saw a engine that has been running Royal Purple Synthetic and it was one of the cleanest engines I have ever taken apart so I may switch to it with my next oil change.
And of course there are a million others.
So let the raging begin